Killed in the crash were two top figures in the security apparatus of the authoritarian Lao government: the deputy prime minister, Douangchay Phichit, and Thongbane Sengaphone, the minister of public security, according to two Lao diplomats.

For a Communist party that relies on force and intimidation to stay in power, the loss of what were arguably the two most powerful people in the security apparatus was a significant blow.

The governor of Vientiane province was also killed in the crash.

In addition to his post as deputy prime minister Mr. Douangchay was defense minister and a member of the Politburo, the highest decision-making body of the Communist party. Mr. Thongbane, the public security head, was feared in the country and was said to be one of the officials leading a crackdown against dissent over the past year and half.

That crackdown included the disappearance of the most prominent civic leader in the country, Sombath Somphone, a United States-trained agriculture specialist who led efforts to liberalize the hermetic communist leadership.

Mr. Sombath was stopped at a police checkpoint in Dec. 2012 and has not been seen again.

The Lao news agency posted photos to a web site Saturday showing the mangled wreckage of the plane, a Russian-made Antonov AN-74TK300.

The news agency, citing a statement from the prime minister’s office, said it was a Laotian Air Force aircraft and it had crashed in Nadi village, west of the Xiangkhouang airport and not far from a major archeological site of prehistoric carved stone vessels, the Plain of Jars.

The authorities were “helping to rescue the survivors,” the news agency said, without offering details on the number of people killed.

The plane was traveling from the capital, Vientiane, to the mountainous northeastern province of Xiangkhouang, where the officials were due to attend a military ceremony.

State television in Laos showed footage of rescue workers recovering debris from the aircraft, which appeared to have crashed in a jungle-covered area.

A news presenter said the crash occurred at around 7 a.m. “The cause of the plane crash is still unknown,” the presenter said.

ALao Facebook page showed images of thick black smoke rising up near what appeared to be an airport runway. The images could not be independently confirmed.

The crash was the second in Laos in the last year. Last October 49 people were killed when a Lao Airlines flight crashed in the south of the country.

The Foreign Ministry in neighboring Thailand said it “received reports” about the crash.

“There were about 20 passengers on board of which most were of high stature,” said Sek Wannamethee, a spokesman for the Thai Foreign Ministry.